Optical switches formed on a substrate are known. Because of their reduced size, microelectromechanical (MEMS) technology is employed to provide the actuation to cause switching. FIG. 1 is a top view of a switch 10 formed on a substrate 12 according to the prior art. The switch 10 includes a mirror 14 which can be moved in and out of an intersection region 15 by MEMS actuators (not shown). FIG. 1 shows the mirror located in the intersection region 15. The switch also includes a first alignment groove 16, a second alignment groove 18, a third alignment groove 20 and a fourth alignment groove 22. Each alignment groove 16-22 has a central axis 24. Each alignment groove is dimensioned to receive a piece of fiber or waveguide therein (not shown).
The first and the fourth alignment grooves 16, 22 hold fiber or waveguides that form the inputting channels of the switch. The second and third alignment grooves 18, 20 hold fiber or waveguides that form the receiving channels of the switch. Depending upon the position of mirror 15, inputting channel 16 may be coupled to one of either receiving channels 18, 20. The same is true for inputting channel 22.
The switch is a 2xc3x972 switch. If a beam is input into a fiber or waveguide located in the first alignment groove 16 and the mirror 14 is retracted from the intersection region 15, the beam passes straight through the intersection region 15 and is output from a fiber or waveguide positioned in the third alignment groove 20. Now if the mirror 14 is positioned in the intersection region 15, the beam is reflected by the mirror to a fiber or waveguide located in the second alignment groove 18. The beam, however, is offset from the central axis 24 of the second alignment groove 18 as indicated by line 26. The reason for this is that the mirror has a thickness associated therewith. The thickness of the mirror offsets the beam""s path from the central axis 24 of the groove 18 receiving the beam after the beam is reflected by the mirror 14.
Similarly, if a beam is input into a fiber or waveguide located in the fourth alignment groove 22 and the mirror 14 is retracted from the intersection region 15, the beam passes straight through the intersection region 15 and is output by a fiber or waveguide positioned in the second alignment groove 18. If the mirror is located in the intersection region 15, the beam is reflected into a waveguide or fiber located in the third alignment groove 20. Because of the thickness of the mirror, however, the beam is offset from the central axis 24 of the third alignment groove 20.
This offset creates several disadvantages. First, the offset causes higher insertion loss than the case when the mirror 14 is retracted from the intersection region 15 and the beam travels straight through. This causes an output power differentiation between the straight through beam and. the reflected beam of as much as 1.3 dB. This differentiation is undesirable in optical networks. To overcome this variable, optical attenuators may need to be added to obtain uniform outputs, however, such a remedy results in higher costs and more complicated designs.
Thus, it is desirable to provide an optical switch that substantially reduces or eliminates offset in the reflected beam. In addition, it is desirable to provide an optical switch that substantially reduces or eliminates the offset without additional structure thereby simplifying the design of the switch. Also, it is desirable to provide an optical switch that has a simple design which is amenable to formation by batch processes.
According to a first aspect of the present invention, there is provided an optical switch that includes a substrate having a first, second, third and fourth edge and a center region. Located on the substrate are a first, second, third and fourth alignment grooves. The first alignment groove extends from the first edge of the substrate to the center region of the substrate and has a first center axis that extends down the center of the first alignment groove. The second alignment groove extends from the second edge of the substrate to the center region of the substrate where the second edge of the substrate opposes the first edge of the substrate. The second alignment groove has a second center axis that extends down the center of the second alignment groove, and the second center axis is offset from the first center axis. The third alignment groove extends from the third edge of the substrate to the center region of the substrate and has a third center axis that extends down the center of the third alignment groove. The fourth alignment groove extends from the fourth edge of the substrate to the center region of the substrate and has a fourth center axis that extends down the center of the fourth alignment groove, and the fourth center axis is offset from the third center axis.
According to a second aspect of the invention, there is provided an alignment structure for an optical switch. The structure includes a first, second, third and fourth groove disposed in a substrate. The first groove extends from a first end to an intersection region, the second groove extends from a second end located remotely from the first end to the intersection region, the third groove extends from a third end located remotely from the first and second ends to the intersection region, and the fourth groove extends from a fourth end located remotely from the first, second, and third ends to the intersection region. The first and second groove meet in the intersection region and the second groove is offset from the first groove and the third and fourth groove meet in the intersection region and the fourth groove is offset from the third groove.
According to a third aspect of the invention, there is provided a method of making an optical switch. The method includes the steps of:
forming a first alignment groove on a substrate wherein the first alignment groove extends from the first edge of the substrate to the center region of the substrate, the first alignment groove having a first center axis that extends down the center of the first alignment groove;
forming a second alignment groove on the substrate wherein the second alignment groove extends from the second edge of the substrate to the center region of the substrate, wherein the second edge of the substrate opposes the first edge of the substrate, the second alignment groove having a second center axis that extends down the center of the second alignment groove wherein the second center axis is offset from the first center axis;
forming a third alignment groove on the substrate wherein the third alignment groove extends from the third edge of the substrate to the center region of the substrate; the third alignment groove having a third center axis that extends down the center of the third alignment groove; and
forming a fourth alignment groove on the substrate wherein the fourth alignment groove extends from the fourth edge of the substrate to the center region of the substrate, the fourth alignment groove having a fourth center axis that extends down the center of the fourth alignment groove wherein the fourth center axis is offset from the third center axis.